WO2020249749A1

WO2020249749A1 - Moisture trap for a device measuring a component in exhaled breath

Info

Publication number: WO2020249749A1
Application number: PCT/EP2020/066333
Authority: WO
Inventors: Bal JOHAL; Helen Westbrook
Original assignee: Circassia AB
Current assignee: Niox AB
Priority date: 2019-06-14
Filing date: 2020-06-12
Publication date: 2020-12-17
Anticipated expiration: 2021-12-14
Also published as: CN211927449U

Abstract

A moisture trap is comprises a filter material (8) and desiccant material (10) adapted for positioning inside a single-use patient mouthpiece (4). Said device can further comprise a perforated foil (11, 14) distributing the flow of exhaled air through the desiccant material. The moisture trap can be a separate item or an integrated part of a patient mouthpiece.

Description

Moisture trap for a device measuring a component in exhaled breath

Technical field

[001] The present disclosure relates to the field of diagnostic measurement of endogenous nitric oxide (NO) in exhaled breath, devices for performing such measurements, and in particular to a moisture trap for preventing the build-up of condensate in such devices.

Background

[002] The discovery of endogenous NO in exhaled air and its use as a diagnostic marker of inflammation dates back to the early 1990-ties (See e.g. international patent applications WO 9S/05709 and WO 95/02181). Today, the significance of endogenous NO is widely recognized, and the concentration of NO in exhaled breath, or fractional exhaled nitric oxide (FeNO), can help identify allergic/eosinophilic inflammation, and thereby support a diagnosis of asthma when other objective evidence is lacking.

[003] NIOX^® (AEROCRINE AB, Sweden) was the first tailor-made NO analyser for routine clinical use with asthma patients. This first device, which was based on chemiluminescence for the detection of nitric oxide, has been followed by NIOX MINO^® (CIRCASSIA AB, Sweden) and VERO^® (CIRCASSIA AB, Sweden), both based on electrochemical detection.

[004] In the summer of 1997, the European Respiratory Journal published guidelines (ERS Task Force Report 10:1683-1693) for the standardisation of NO measurements to allow their rapid introduction into clinical practice. Soon thereafter, the American Thoracic Society (ATS) published guidelines for clinical NO measurements (American Thoracic Society,

Medical Section of the American Lung Association: Recommendations for standardized procedures for the online and offline measurement of exhaled lower respiratory nitric oxide and nasal nitric oxide in adults and children, in Am 1 Respir Crit Care Med, 1999; 160:2104- 2117). These recommendations have been updated, and in 2018, the Global Initiative for Asthma (GINA) published a Global Strategy for Asthma Management and Prevention (Full text available on www.ginasthma.org). It however remains a requirement that the patient must exhale for a certain period of time (at least 10 sec) and at a relatively constant flow, preferably at a flow of 50 ml/s ±5 ml/s. [005] Endogenous NO is present in trace quantities in exhaled air, low values being 25 ppb (parts-per-billion) or less. Values between 25 ppb and 50 ppb should be interpreted cautiously and with reference to the clinical context, whereas values over 50 ppb are held to indicate eosinophilic inflammation or asthma. When detecting and quantifying so low concentrations, the sensitivity and accuracy of measurement becomes paramount and variations in for example temperature, humidity, and flow can influence the measurement.

[006] Maintaining an accurate exhalation flow into the device is critical to maintain the accuracy of the FeNO measurement. To this end, most diagnostic devices for the

measurement of FeNO have built-in pressure sensors / flow sensors. One example is the use of differential pressure transducers, where the pressure drop across an orifice or constriction in a flow channel is measured and the flow rate calculated. The flow rate of the patient exhalation is measured, and the patient can receive feed-back which assists in maintaining the exhalation flow within the required interval (50 ml/s ±5 ml/s). Performing a correct exhalation into the device however requires some practice. While some patients manage already on the first or second try, others require repeated attempts before a successful measurement is achieved.

[007] Exhaled breath contains water vapour. The average amount of water vapour in a ten second exhalation at 24 °C at 60 % relative humidity (RH) is 448 pg. If a patient has difficulties performing a correct exhalation, and needs to try again and again, the same patient will exhale humid breath into the device repeatedly within a short period of time, which may result in the build-up of moisture in the device.

[008] Even with successful exhalations, there are other reasons for an accumulation of moisture to occur. In some clinical settings, the frequency of use is very high. There is anecdotal evidence that some devices for measuring exhaled NO are used by up to 80 patients in a single day. Additionally, as the devices are used at clinics all over the world, some will inevitably be used in humid climates, such as southern and eastern China, parts of the southern USA, parts of Australia, India, Brazil etc. Moisture may however be a problem also on colder climates. As the exhaled breath always contains moisture, this will condensate when it comes in contact with a cold surface.

[009] These factors alone, and in combination, may lead to the build-up of moisture in the devices. This is a problem, because once the cumulative moisture in the device reaches a certain level, the moisture starts to condensate and form water droplets. Water droplets risk causing blockage of the tubes leading to the pressure sensors used for measuring the flow rate. If the water enters the pressure sensors, device components may be damaged.

[010] Currently, some devices use an algorithm to estimate the amount of moisture in the device and forces the it to shut down when the estimated moisture level becomes too high to allow it to dry out. Regardless if the device is used with a high frequency, i.e. either repeatedly by the same individual, or used sequentially by separate individuals with short and in particular in humid climates, such algorithms limit the number of measurements that can be performed before the device shuts down. This is not satisfactory, and there is a need for preventing moisture from entering the device.

[Oil] At the same time, the sample reaching the electrochemical sensor should not be dried to an extent that it affects the sensitivity of the sensor. Electrochemical sensors for detecting nitric oxide frequently have a certain cross-sensitivity for CO2, which increases with reduced moisture in the sample. In fact, some sensors need at least 20 % RH to function correctly.

[012] There are known solutions for catching moisture in exhaled breath, for example by leading the flow of exhalation over a surface which is colder than the exhaled breath, resulting in the moisture condensing on the surface. Examples include the device disclosed in WO 2004/058125 titled "Disposable hand-held device for collection of exhaled breath condensate" and the device shown in WO 2017/153755 titled "Exhaled breath condensate collection device and kit of parts therefor." These are effective in applications where there is an interest in analysing the condensate itself, as it contains different substances that may be diagnostic markers. However, when the analyte is in the gas phase, the condensate needs to be disposed of, and this has to be done safely, considering that the condensate can contain infectious matter, such as viruses and bacteria and thus constitute a bio-hazard.

Summary

[013] The present disclosure makes available a new, practical and surprisingly effective solution to the aforementioned problems. According to a first aspect, the present disclosure makes available a moisture trap adapted for use with a device for diagnostic measurement of nitric oxide (NO) in exhaled breath said device comprising a handpiece for receiving exhaled breath, a channel leading from said handpiece into said device, a flow sensor and/or a pressure sensor measuring the flow and/or pressure of exhaled breath in said channel, and a sensor or sensing element that produces a detectable signal corresponding to the concentration of nitric oxide in said exhaled breath, wherein said moisture trap comprises a particle filter material (8) and a desiccant material (10), wherein said desiccant is arranged next to said particle filter material and adapted for positioning inside a mouthpiece or patient filter, or between said mouthpiece and said channel, for example adjacent to said mouthpiece.

[014] According to an embodiment, the desiccant material is chosen from molecular sieves, bentonite clay, silica gel beads, silica gel grains, granules or particles, and combinations thereof. The amount of desiccant material is dependent on the type of material, but is preferably chosen in the interval of 0.1 g to 20 g, more preferably about 1 g to about 10 g, and most preferably about 1 - 5 g.

[015] According to an embodiment, freely combinable with the above, the particle filter material is chosen from natural and synthetic fibers, such as but not limited to cellulose, polypropylene and glass fiber materials, or combinations thereof.

[016] According to another embodiment, freely combinable with the above, the particle filter material encloses said desiccant material forming a composite filter pad.

[017] According to another embodiment, freely combinable with the above, the moisture trap includes a perforated foil on at least one side, the perforations arranged to distribute the flow of exhaled breath evenly through the filter.

[018] According to yet another embodiment, freely combinable with the above, the moisture trap has a perforated foil on both sides thereof, the perforations being arranged substantially around the periphery of one foil, and substantially in the centre of the other foil.

[019] According to another embodiment, freely combinable with the above, the foil is made of metal or polymer.

[020] According to yet another embodiment, freely combinable with the above, the moisture trap is adapted for placement between a patient filter / mouthpiece and a handpiece. [021] According to yet another embodiment, freely combinable with the above, the moisture trap is integrated into a patient filter / mouthpiece.

[022] According to yet another embodiment, freely combinable with the above, the moisture trap is a single use item, intended for use with one patient and discarded after use.

Short description of the drawings

[023] The invention will be described in closer detail in the following description, non limiting examples, and claims, with reference to the attached drawings in which:

[024] Figure 1 is a photograph showing one example of a device for diagnostic

measurement of NO (here the commercially available device NIOX VERO^®, CIRCASSIA AB, Sweden), comprising a body 1, a handle or handpiece 2, a tube S connecting said handle to the body, and a patient mouthpiece 4.

[025] Fig. 2 (a) and (b) show an example of a patient mouthpiece 4, in two perspective views, where (a) shows an opening 5 which the patient can close his/her lips around, and exhale into. In the second view (b) the inside of said mouthpiece is shown, illustrating lugs 6 for engaging with the handle. The exact design of a mouthpiece can vary, but it needs to fill the basic function of offering a hygienic, single-use interface for the patient to breath into, preventing cross-contamination of the device and the transmission of disease between patients.

[026] Fig. B shows schematically a moisture trap 9 according to an aspect of the present invention, here a bag or pouch of a filter material 8 shown in cross-section containing a desiccant material 10 in granulate or particulate form.

[027] Fig. 4 shows schematically an exploded view of another a moisture trap 90 according to an aspect of the present invention, where a filter material bag 8 is surrounded by two perforated foils, where on one foil 11 a number of perforations 12 are arranged around the perimeter of the foil, while on another foil 14 a number of perforations 15 are positioned near the centre. The perforations are not drawn to scale, and the exact number, size and position of the perforations may vary. [028] Fig. 5 shows a moisture trap 900 according to an embodiment, where an outer layer of filter material covers the foil on one or both sides of the moisture trap, here shown by layers 16 and 17, which may be of the same material, or different.

[029] Fig. 6 shows a cross-section of a moisture trap 90, where a flow path is indicated by white arrows, entering through a peripheral perforation 12 of foil 11, passing through the filter material 8 and the desiccant 10, and exiting through a central perforation 15 of foil 14.

[030] Fig. 7 is a graph illustrating the build-up of moisture during use of a test set-up simulating the use of an apparatus for the diagnostic measurement of NO. Time is plotted along the x-axis where the brackets indicate the duration of exhalations, typically 10 sec. One shorter, unsuccessful exhalation is indicated with *. The relative humidity is plotted along the y-axis, and a moisture limit shown as a horizontal dotted line. The dotted curve to the left and the dashed curve to the right show the moisture build-up at 85 % RH and 60 % RH respectively. At the higher humidity, the accumulated moisture reaches a pre-set limit already after three successful and one unsuccessful exhalation.

[031] Fig. 8 is a graph showing the weight increase of different desiccant arrangements normalised for 360 uses. The two uppermost curves correspond to 19 g and 14.3 g of desiccant, and the three lower curves correspond to 1 g, 2.7 g, and 2.8 g of desiccant. The results show that while a high amount of desiccant exhibits the largest and most enduring weight increase, also a small amount works well. Here, already 1 g of desiccant works well.

[032] Fig. 9 schematically shows, in partial cut-out view, how a handle 2, 200 having a mouthpiece 4, 400, holds a moisture trap 9, 90, 900. The handle is connected to a tube 3, 300 leading to a device 1, 100 for diagnostic measurement of endogenous nitric oxide (NO) in exhaled breath, comprising a pressure sensor 110 and a sensor or element 120 for the detection and quantification of NO.

Detailed description

[033] Before the present invention is described, it is to be understood that the

terminology employed herein is used for describing particular embodiments only and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims and equivalents thereof. [034] It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[035] The term "mouthpiece" is here used to describe the physical interphase between a patient and an apparatus for measuring endogenous NO in exhaled breath. When performing a test, the patient exhales into said mouthpiece. A mouthpiece is for single-use and discarded when the patient has performed successful exhalations and a FeNO value has been obtained.

[036] The term "handle" or "handpiece" refers to an element of a set-up for diagnostic measurement of endogenous nitric oxide (NO) in exhaled breath, which a patient can comfortably hold when exhaling. The handle constitutes a physical interface between the patient and the device, in that the handle holds in one end a mouthpiece or patient filte, and in the other end connects to the device for NO measurement.

[037] According to a first aspect, the present disclosure makes available a moisture trap (9, 90, 900) adapted for use with a device (1) for diagnostic measurement of nitric oxide (NO) in exhaled breath said device comprising a handpiece (2) for receiving exhaled breath, a channel (3) leading from said handpiece into said device (1), a flow sensor and/or a pressure sensor (110) measuring the flow and/or pressure of exhaled breath in said channel, and a sensor or sensing element (120) that produces a detectable signal corresponding to the concentration of nitric oxide in said exhaled breath, wherein said moisture trap (9, 90, 900) comprises a particle filter material (8) and a desiccant material (10), wherein said desiccant is arranged next to said particle filter material and adapted for positioning inside a mouthpiece or patient filter (4), or between said mouthpiece (4) and said channel (3).

[038] The sensor or sensing element (120) which produces a detectable signal

corresponding to the concentration of nitric oxide can be one of many different types of sensors or sensing elements, the most preferred being an electrochemical sensor. Other techniques for detecting and quantifying nitric oxide include chemiluminescence, ultrasonic sensors, graphene-hemin sensors, optical / colorimetric sensors based on e.g. solgel- trapped reagents changing color in the presence of nitric oxide. [039] According to an embodiment of the above aspect, said desiccant material is chosen from molecular sieves, bentonite clay, silica gel beads, silica gel grains, granules or particles, and combinations thereof. Preferably the desiccant material is a food grade silica gel material, either in bead, grain or granular form. Silica gel is available in many different qualities from numerous suppliers, for example from Sigma-Aldrich^® (MERCK KGaA, Darmstadt, Germany).

[040] The amount of desiccant material is dependent on the type of material, but is preferably chosen in the interval of 0.1 g to 20 g, more preferably about 1 g to about 10 g, and most preferably about 1 - 5 g. Surprisingly, already a small amount of desiccant material, such as 1 g of a food grade silica gel desiccant, proved to be effective.

[041] According to an embodiment of the above aspect, said particle filter material is chosen from natural and synthetic fibers, such as cellulose, polypropylene and glass fiber materials, or combinations thereof. The filter material can be a woven or non-woven material, for example a woven or non-woven fabric, a filter paper or a porous membrane. Particle filter materials are available from different suppliers, for example GVS Filtration Inc., Findlay, OH, USA.

[042] According to an embodiment of the above aspect, said particle filter material (8) encloses said desiccant material (10) forming a composite filter pad (9). The particle filter can be shaped as a bag or pouch, and folded, glued or hot melted to form a closed pad containing the desiccant material. Two round pieces of filter material can be joined at the edges, for example glued or heat sealed to form a pad enclosing the desiccant material. The filter material can also be bonded across the pad in a quilt-like fashion, minimizing movement of the desiccant material.

[043] According to a preferred embodiment, freely combinable with any of the above embodiments, said moisture trap (90, 900) includes a perforated foil (11, 14) on at least one side, the perforations arranged to distribute the flow of exhaled breath evenly through the filter.

[044] According to another preferred embodiment, freely combinable with any of the above embodiments, said moisture trap (90, 900) has a perforated foil (11, 14) on both sides, the perforations (12, 15) being arranged substantially around the periphery of one foil, and substantially in the centre of the other foil. Said holes can be punched or laser cut using techniques well known to a person skilled in the art. The exact size, number and placement of the holes can be optimized to distribute the flow of exhaled air through the entire volume of desiccant material. Importantly the holes on one foil are offset in relation to the holes on the other foil, extending the flow path of the airflow through the filter pad.

[045] In the above embodiments, said foil is made of metal or polymer, for example aluminium foil or a plastic foil.

[046] According to a preferred embodiment, freely combinable with any of the above embodiments, said moisture trap (9, 90, 900) according to claim 1, adapted for placement between a patient filter / mouthpiece (4) and a handpiece (2).

[047] Preferably the moisture trap (9, 90, 900) according to any of the above

embodiments, is integrated into a patient filter / mouthpiece (4). Integrated here means that from the perspective of the user, the patient filter / mouthpiece comes with a moisture trap in place, and that the user only needs to affix one item to the handle before performing or instructing a patient to perform the exhalation. When the moisture trap is integrated into a patient filter, the filter material (8) and optionally the foil or foils (11, 14) and optionally the filter or filters (16, 17) can seal against the inside of the patient filter along the periphery of the moisture trap.

[048] Integrated can also mean that the moisture trap is a separate entity, but that it is inserted into the mouthpiece, for example pressure-fitted or snap-fitted into the

mouthpiece, and for all practical purposes, the end-user perceived this as one item.

[049] With reference to Fig. 5, it is contemplated that the outermost filter or filters (16,

17) and in particular the layer on the proximal side of the moisture trap (900) serves to capture droplets of moisture condensing on the foils, and in particular on the first perforated foil (11).

[050] According to an embodiment combinable with any one of the above, the moisture trap is a single use item, intended for use with one patient only and discarded after use.

[051] The moisture trap is preferably produced in a sanitary and dry environment, and then assembled and enclosed in water-tight packaging, preferably a polymer film, a metallized polymer film or the like, to guarantee the hygiene and sufficient shelf-life of the moisture trap. When the moisture trap is integrated in a mouthpiece or patient filter, the moisture trap does not require its own packaging, as the combined mouthpiece and moisture trap assembly will be packaged in water-tight packaging, preferably a polymer film, a metallized polymer film or the like, to guarantee its hygiene and sufficient shelf-life. When the moisture trap is stored separately from the mouthpiece, each is packaged separately, and has to be removed from its packaging. The moisture trap is then placed into an unused mouthpiece and the mouthpiece is attached to the handle shortly before a patient performs the exhalation.

[052] When a patient exhales through the mouthpiece into the handpiece, through which the exhalation is led further into the device for diagnostic measurement of nitric oxide, the exhalation phase is only 10 seconds. It was shown by the inventors that, during exhalation, only a fraction of the moisture in the exhaled air is absorbed by the desiccant. Instead, the moisture condensates on the surfaces of the handpiece, and when the perforated foils are included in the moisture trap, on the surfaces of these foils. However, as the inventive moisture trap is arranged adjacent to the handpiece, this condensed moisture will be absorbed by the desiccant material after conclusion of the exhalation, when the device measures and calculates the concentration of nitric oxide in the exhaled breath. This phase, after the patient has exhaled into the device, through the mouthpiece and the handpiece, can last 30 seconds or longer. The mouthpiece with the moisture trap is left in place until a successful exhalation has been performed, and the result (the measured NO concentration) displayed. During this time, the moisture trap surprisingly acts to dry the inner surfaces of the handpiece, where moisture has condensed during the exhalation. This is a major advantage, as the condensed moisture is a more serious problem than the moisture as such. When condensing on colder surfaces in the handpiece, the moisture forms droplets which can travel in the flow channel / tubing and risk blocking and ultimately damaging

components such as the flow/ pressure sensors. The moisture trap thus surprisingly serves multiple functions, both as a particle filter protecting the patient during inhalation, and "protecting" the device when the patient exhales, and the desiccant sandwiched between two layers of filter material serves to dry - to some extent - the exhalation air, but importantly also serves to absorb and thus dry out the handpiece after the exhalation itself, between subsequent exhalations. At the same time, the moisture trap does not completely dry out the exhaled breath, which is an advantage as at least one type of sensors, the electrochemical sensors, require about 20 % RH for proper function.

[053] Another advantage of the solution disclosed herein is that the moisture trap is easy to remove and replace, and also economical to manufacture. By integrating the particle filter / patient filter into the moisture trap, several different needs are met. The particle filter / patient filter creates a barrier between the device and the patient, preventing any transfer of bacterial or viruses via the device. The filter material also fills a dual function as filter and as holder or envelope for the desiccant material. This makes it possible to replace currently used commercial patient filters with the combined filter and desiccant assembly with no or minimal alterations of the mouthpiece. In the alternative embodiment, where the moisture trap is an integrated part of the mouthpiece, the small desiccant volume makes it possible to include the inventive moisture trap in existing mouthpieces without any significant alteration of their design.

Examples

Comparative Example. Dew-catcher

[054] A mechanical dew catcher was constructed by BD-printing and assembling parts creating a convoluted flow path and a condensation chamber. The dew catcher was connected to the tube 3 between the handle 2 and the body 1 of a device (a NIOX VERO^®, shown in Fig. 1). 20 dew catchers were tested in clinical use and found to function as intended, i.e. a significant quantity of moisture was collected in the condensation chamber. This experimental mechanical dew catcher however had to be opened, emptied and cleaned daily. The emptying and cleaning received very negative feedback from the users. Due to a potential biohazard risk, special care was necessary when emptying and disposing of the collected moisture.

Example 1. Testing pressure drop

[055] In an experimental set-up, 2 g desiccant material was included in a "bag" of filter paper as shown in Fig. 3 and tested in a standard mouthpiece of a device as shown for example in Fig. 1 and Fig. 9 to determine if the moisture trap assembly obstructed the flow. Table 1. Pressure drop across breathing handle

[056] The results show that a moisture trap can be incorporated in existing mouthpieces without causing any significant pressure drop.

Example 2. Moisture collection capacity

[057] A test set-up was constructed as follows: A NIOX VERO^® handle and mouthpiece was connected to a sealed climate chamber producing moist, warm air at approx. 35 °C and 97 % RH to simulate a patient's breath. A vacuum pump was used to draw air at a constant rate of 3 l/min, the flow adjusted manually using a flow meter and a finely adjustable flow control. Directly when exiting the handle and mouthpiece, the flow of moist air was led into a cooled condensate collection chamber. A standard "breath" or device "use" was taken to be 10 seconds in duration, as per current NIOX VERO^® user manual. A timer was used to ensure that the duration of flow was equivalent to the number of exhalations required by each individual test. Different moisture traps containing different amounts of desiccant were inserted in a mouthpiece, modified when necessary, and attached to the handle. The handle, tube and moisture traps were weighed before and after 40, 60, 120 and 180 seconds of continuous flow, and after completion of the experiment, and the weight increase taken as a measure of their effectiveness. A handle with a standard mouthpiece IB

(no desiccant) was used as baseline. All tests were conducted in accordance with this test method.

[058] Silica gel (SiCh) was tested in the form of grains or beads having a bead size of 1.4 - 3.0 mm (Clariant Co., Charlotte, NC, USA). The beads are bright orange when dry and turn dark blue when fully saturated with moisture.

[059] Different amounts of silica gel were weighed and loaded directly into a standard mouthpiece or packaged into a pad 9 consisting of microfilter 8 on two sides, for example as shown in Fig. 3. The tested amounts of desiccant were 0.9 g, 2.6 g, 2.7 g, 2.8 g, 14.3 g and 19.0 g which represents the maximum amount of desiccant that fits the current design of the mouthpiece. An unmodified mouthpiece and handle were used to create the baseline. The 19.0 g set-up was tested for up to 780 uses or 7800 seconds of flow with the desiccant in place. This represents an extreme case and the experiment as performed in order to see when the desiccant will stop absorbing moisture from the air. The results showed that when using 14.3 g the desiccant had not fully turned blue even after 180 uses (1800 seconds) and when using 19.0 g, there was remaining desiccant capacity still after 360 uses (3600 seconds). An example of the results is shown in Fig. 8.

Example 3. Modification of flow path

[060] In this example, a perforated cover or foil as shown in Fig. 4, items 11 and 14, was used to investigate if the efficacy of the moisture trap could be improved by modifying the flow path of exhalation through the bulk of desiccant. As shown in Fig. 4, the perforations were arranged along the perimeter of the foil. The experiment showed that a moisture trap with 2.7 g desiccant and a perforated foil performed better than 2.8 g desiccant without said foil. This is due to the more efficient flow path, which exposes the flow of breath to more surface area of the desiccant and hence more moisture is absorbed. It is contemplated that also the foil itself acts as a surface on which moisture condensates.

Example 4. Amount of desiccant

[061] The combined mouthpiece and patient filter are intended to be used by one patient only and discarded after use. As it is likely to be used for a maximum of 5 - 10 exhalations, even assuming that occasional patients have difficulties performing a correct exhalation, it was investigated if the amount of desiccant could be minimized. It was seen that for the first 100 seconds, corresponding to 10 uses, the performance of a moisture trap assembly containing only 0.9 g desiccant was practically equal to that of 19.0 g desiccant.

[062] In summary, the experiments showed that incorporating even a small amount of desiccant into a microfilter pouch 8 placed in a mouthpiece had a significant effect of removing moisture and thus preventing moisture from entering the device, where it could risk accumulating and potentially damage components of the device or influence the accuracy of the measurements.

Example 5. Relative humidity measurement

[063] A humidity sensor (Binder GmbH, Tuttlingen, Germany) was connected downstream in the experimental set-up described in Example 2, using a moisture trap including 2.6 g desiccant. The humidity in the system was measured every 20 seconds for 6 minutes at a flow of 3 l/min. The result showed that the RH rises continuously even though the desiccant unit is extracting moisture from the air upstream of the measurement point. The results show that inclusion of a moisture trap including desiccant does not make the air reaching the electrochemical sensor too dry. In fact, the use of a desiccant ensures helps to stabilize the RH in the air reaching the sensor.

[064] Without further elaboration, it is believed that a person skilled in the art can, using the present description, including the examples, utilize the present invention to its fullest extent. Also, although the invention has been described herein with regard to its preferred embodiments, which constitute the best mode presently known to the inventors, it should be understood that various changes and modifications as would be obvious to one having the ordinary skill in this art may be made without departing from the scope of the invention which is set forth in the claims appended hereto.

[065] Thus, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

1. A moisture trap (9, 90, 900) adapted for use with a device (1) for diagnostic

measurement of nitric oxide (NO) in exhaled breath said device comprising a handpiece (2) for receiving exhaled breath, a channel (3) leading from said handpiece into said device (1), a flow sensor and/or a pressure sensor (110) measuring the flow and/or pressure of exhaled breath in said channel, and a sensor or sensing element (120) that produces a detectable signal corresponding to the concentration of nitric oxide in said exhaled breath, characterized in that said moisture trap (9, 90, 900) comprises a particle filter material (8) and a desiccant material (10), wherein said desiccant is arranged next to said particle filter material and adapted for positioning inside a mouthpiece or patient filter (4), or between said mouthpiece (4) and said channel (3).

2. The moisture trap according to claim 1, wherein said desiccant material is chosen from molecular sieves, bentonite clay, silica gel beads, silica gel grains, granules or particles, and combinations thereof.

3. The moisture trap according to claim 1, wherein said particle filter material is chosen from natural and synthetic fibers, such as cellulose, polypropylene and glass fiber materials, or combinations thereof.

4. The moisture trap according to claim 1, wherein said particle filter material (8) encloses said desiccant material (10) forming a composite filter pad (9).

5. The moisture trap according to claim 1, wherein said moisture trap (90, 900) includes a perforated foil (11, 14) on at least one side, the perforations arranged to distribute the flow of exhaled breath evenly through the filter.

6. The moisture trap according to claim 1, wherein said moisture trap (90, 900) has a perforated foil (11, 14) on both sides, the perforations (12, 15) being arranged substantially around the periphery of one foil, and substantially in the centre of the other foil.

7. The moisture trap according to claim 5 or 6, wherein said foil is made of metal or polymer.

8. The moisture trap (9, 90, 900) according to claim 1, adapted for placement between a patient filter / mouthpiece (4) and a handpiece (2).

9. The moisture trap (9, 90, 900) according to claim 1, forming an integral part of a patient filter / mouthpiece (4).

10. The moisture trap according to any one of the claims above, wherein said moisture trap is a single use item, intended for use with one patient and discarded after use.